1. Field of the Invention
The present invention relates to a semiconductor circuit having a buffer function.
2. Related Background Art
Hitherto, a semiconductor integrated circuit using a Bi-CMOS process has been constructed as shown in FIG. 4A.
In the diagram, reference numerals 1 to 4 denote bipolar type transistors, 5 and 6 indicate constant current devices comprising MOS FETs, and 10 and 11 represent lines connected to one terminal of a power supply. When an input 14 is at the high level, the transistor 3 is turned off and the transistor 4 is turned on, so that the transistor 1 is turned on and the transistor 2 is turned off and the output is set to the high level. When the input is at the low level, the transistor 3 is turned on and the transistor 4 is turned off, so that the transistor 1 is turned off and the transistor 2 is turned on and the output is set to the low level.
As mentioned above, the circuit of FIG. 4A functions as a buffer as shown in FIG. 4B.
Therefore, for instance, as shown in FIG. 5, when a plurality of circuits of FIG. 4A are used to switch input signals, a multiplexer to select one of a plurality of buffer circuits is further necessary, so that the circuit scale enlarges and the electric power consumption increases. Further, there is a problem such that the electric power is consumed even in the other buffers which are not selected by the multiplexer.